Objective To study the relationship between alpha-fetoprotein (AFP),proliferation cell nuclear antigen (PCNA) in amniotic fluid and spontaneous abortion through detecting the level of AFP and PCNA in spontaneous abortion patients and normal pregnancy women. Methods sixty-four spontaneous abortion patients were collected as study group,who was further divided into 2 subgroups corresponding to threatened abortion with 32 patients and missed abortion with 32 patients. The other 32 cases of normal pregnancy were as control group. The level of AFP in amniotic fluid was determined with chemiluminescence immunoassay. The expression of PCNA in placenta tissue was examined SP immune-histochemistry technique. Results The level of amniotic fluid AFP was(8 356±607)μg/L in normal pregnancy group,(7 024±498) μg/L in threatened abortion group,(5 638±533)μg/L in missed abortion group respectively. There were significant differences among three groups (P0.05). The positive rate of PCNA expression was(56.49±2.17)% in normal pregnancy group,(48.96±1.43)% in threatened abortion group,(39.53±1.74)% in missed abortion group recpectively. There were significant differences among three groups (P0.05). Proliferation index(PI) of PCNA was closely related to level of amniotic fluid AFP in every group (P0.05). Conclusion The results showed that low expression of AFP and PCNA may have relationship with spontaneous abortion.